In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
Mining and construction machines are being designed with progressively faster cutter drum and chain speeds. These advancements are making it more difficult to retain tools in their respective holders, such as a tool block or a bore of a rotating drum. For this reason, friction sleeve retainers are becoming less effective in retaining tools. Many industries are starting to progress towards rear retention to hold tools in holders.
Rear retainers are typically used in applications where the user needs maximum retention. These retainers are separate, loose parts that are inserted in a retaining feature, such as a groove, on the portion of the tool shank that projects beyond the rear of the tool block.
Rear retainers have certain limitations. Rear retainers can be difficult to assemble and remove due to limited access behind the holder. In order to assemble a typical external retainer onto a tool, a certain amount of clearance is required between the rear of the holder and the groove in the tool shank. This clearance can allow unnecessary freedom of movement between the tool and holder, causing an unwarranted amount of slapping between the tool shoulder and face of the holder. This slapping can cause excessive wear in the bore and on the face of the holder, reducing the lifetime of both parts.
Certain retainers require special tools (for example, snap rings require special pliers) while others require excessive force (for example, cut washers) during installation and removal. Due to the elastic memory of these retainers, during removal many retainers are prone to “pop” off in any given direction. This can make the removal of these “projectile” retainers dangerous on the job site as well as cumbersome to use if one loses the retainer and needs to find a replacement.